Electrospinning is a process by which sub-micron polymer fibers can be produced using an electrostatically driven jet of polymer solution (or polymer melt). Electrospun fibers are typically collected in the form of non-woven mats, which are of interest for a variety of applications including semi-permeable membranes, filters, composite reinforcement, and scaffolding used in tissue engineering. A characteristic feature of the electrospinning process is the onset of a chaotic oscillation of the electrospinning jet. The current work demonstrates the feasibility of dampening this instability and controlling the deposition of sub-micron polymer fibers (< 300 nm in diameter) on a substrate through use of an electrostatic lens element and collection target of opposite polarity. Real-time observations of the electrospinning process have been made using high-speed, high-magnification imaging techniques. Fiber mat!; and yarns electrospun from polyethylene oxide have been analyzed using wide-angle X-ray diffraction (WAXD). optical microscopy, and environmental scanning electron microscopy (ESEM). (C) 2001 Published by Elsevier Science Ltd.